NVIDIA GeForce GTX 765M SLI vs NVIDIA GeForce 830M vs NVIDIA GeForce 820M

NVIDIA GeForce GTX 765M SLI

The NVIDIA GeForce GTX 765M SLI is a high-end DirectX 11-compatible graphics solution for laptops, consisting of two GeForce GTX 765M. Each card has a 28nm GK106 core based on the Kepler architecture. The clocks for the SLI-setup are identical to a single GTX 765M. With SLI, each card usually renders a single frame (AFR mode). Therefore, it may suffer from micro stuttering in low fps ranges below 30fps. This happens because of irregular delays between two sequential frames.

Architecture

The Kepler architecture is the successor to the Fermi architecture that first appeared in laptops with the GeForce 400M series. The GK106 Kepler core offers five shader blocks, called SMX, that are clocked at the same speed as the central core. In the GTX 765M, only four blocks are activated (= 768 CUDA-Cores for each 765M). Although the Kepler architecture can utilize more shader cores than a Fermi chip, its shaders can be up to twice as power efficient. However, due to the missing hot clock of the shader domain, two shaders of a Kepler chip are of similar speed to one shader of a Fermi chip (as the latter is clocked twice as fast).

PCIe 3.0 is now supported by the mobile Kepler series and an optional Turbo mode can automatically overclock the Nvidia card by a theoretical 15 percent if the laptop cooling system allows it. The implementation of this boost mode is done in the BIOS, but it is ultimately dependent upon the manufacturer of the laptop.

Performance

The graphics performance of the GeForce GTX 765M SLI is about 70 - 80 percent above a single GTX 765M, making it as fast as a single GeForce GTX 680M. Therefore, most games as of 2013 are playable at the highest detail setting and in FullHD resolution. In many cases it is even possible to activate additional anti-aliasing.

Features

The feature set includes support for up to 4 active displays. Furthermore, high resolution monitors of up to 3840x2160 pixels can now be connected using DisplayPort 1.2 or HDMI 1.4a if available. HD-Audio codecs, such as Dolby TrueHD and DTS-HD, can be transmitted via bitstream mode through the HDMI port. However, as most laptops will feature Optimus, the integrated GPU will likely have direct control over the display ports and may limit the feature set available by the Nvidia Kepler cards.

The 5th generation PureVideo HD video processor (VP5) is also integrated in the GK106 core and offers hardware decoding of HD videos. Common codecs such as MPEG-1/2, MPEG-4 ASP, H.264 and VC1/WMV9 are fully supported up to 4K resolutions while VC1 and MPEG-4 are supported up to 1080p. Two streams can be decoded in parallel for features such as Picture-in-Picture. Another novelty is the inclusion of a dedicated video encoding engine similar to Intel QuickSync that can be accessed by the NVENC API.

Power consumption

The power consumption of the GeForce GTX 765M SLI should double that of a single 765M at about 120 - 130 W including the boards and memory. Therefore, the dual cards are well-suited for large desktop replacements.

NVIDIA GeForce 830M

The NVIDIA GeForce 830M is a (lower) mid-range, DirectX 12-compatible graphics card for laptops unveiled in March 2014. It is one of the first cards based on Nvidia's new Maxwell architecture (GM108 chip), but is still manufactured in 28 nm. The 830M offers 256 shader units clocked at 1029 MHz (+ Boost) as well as 2 GB of DDR3 memory (64 bit, 2000 MHz effective).

Architecture

Compared to Kepler, Maxwell has been optimized in several details to increase power efficiency. Smaller Streaming Multiprocessors (SMM) with only 128 ALUs (Kepler: 192) and an optimized scheduler should lead to better utilization of the shaders. Nvidia promises that a Maxwell SMM with 128 ALUs can offer 90 percent of the performance of a Kepler SMX with 192 ALUs. The 830M features a partially deactivated GM108 with just 2 out of 3 SMMs (256 shader cores, 16 TMUs, 8 ROPs, 64-bit interface). 

Another optimization is the massively enlarged L2 cache. The larger size can process some of the memory traffic to allow for a relatively narrow memory interface without significantly reducing performance.

Similar to GM107, the GM108 supports DirectX 12 (Feature Level 11_0 only).

Performance

According to Nvidia, the GeForce 830M is about 25 percent faster than the old GT 730M. Practically, the advantage is a bit smaller and the performance similiar to the old GeForce GT 740M (about 20 percent below the GeForce 840M). Many games of 2013/2014 will run fluently in WXGA resolution (1366 x 768) and medium detail settings. However, very demanding games such as Crysis 3 or Battlefield 4 will require even lower resolutions and/or details.

Features

GM108 integrates the sixth generation of the PureVideo HD video engine (VP6), offering a better decoding performance for H.264 and MPEG-2 videos. Of course, VP6 supports all features of previous generations (4K support, PIP, video encoding via NVENC API). Unfortunately, HDMI 2.0 is still not supported.

Power Consumption

The power consumption of the GeForce 830M should be about 25 Watts or less. Therefore, the 830M is best suited for laptops 13 inches in size or larger. The 800M series also supports Optimus to automatically switch between an integrated graphics card and the Nvidia GPU.

NVIDIA GeForce 820M